WO-A1-85/05553 discloses bacterial cell surface proteins having fibronectin, fibrinogen, collagen, and/or laminin binding ability. Thereby it is shown that different bacteria have an ability to bind to fibronectin, fibrinogen, collagen, and/or laminin. It is further shown that fibronectin binding protein has a molecular weight of 165 kD and/or 87 kD, whereby it is probable that the smaller protein is a part of the larger one.
Fibronectin is a large glycoprotein (M.sub.r ca 450 kd) with two similar subunits, which may vary in molecular size depending on a complex splicing pattern of a precursor mRNA (1). The major function of fibronectin, which is found in body fluids, blood clots and extracellular matrices, seems to be related to the ability of the protein to mediate substrate adhesion of most eukaryotic cells (2, 3, 4, 5.)
In the late seventies, Kuusela found that fibronectin not only interacts with eucaryotic cells but also binds to cells of Staphylococcus aureus (6). Since this observation, a number of pathogenic microorganisms have been shown to bind to fibronectin with a high degree of specificity and a high affinity, such as streptococci (group A, C, and G), coagulase negative staphylococci, E. coli and Treponema pallidum. Fibronectin in the extracellular matrix appears to serve as a substratum also for the adhesion of different microorganisms. The binding of fibronectin may for some microorganisms represent a crucial step in the colonization of host tissue and development of infection.
Several different cell surface components have been implicated as fibronectin receptors on Gram-positive bacteria including lipotechioc acid (8, 9) and protein (10). In previous studies a fibronectin binding protein with a M.sub.r of 197-210 kD has been isolated from S. aureus strain Newman (11, 12) and tentatively identified as a fibronectin receptor. The binding site in fibronectin for eukaryotic cells has been localized to a tetrapeptide (ArgGlyAspSer) in the central portion of each of the two subunits forming the fibronectin, which is different to the binding site of most bacteria so far studied. The bacteria appear to bind to the aminoterminal 29 kDa domain of the fibronectin subunit.
An eukaryotic receptor has been identified as a 140 kDa complex in the cell membrane, whereas the bacterial fibronectin binding protein (FNBP) of Staphylococcus aureus strain Newman has been identified as a 210 kDa protein. From previous studies (SE-A-8702272-9) it has been reported of the cloning, expression and the complete nucleotide sequence of a gene (herein called gene 1) for a FNBP in Staphylococcus aureus.
In the present application the cloning, expression and the nucleotide sequence of a further gene, gene 2, located downstream the previous studied and reported fibronectin binding protein sequence. To further characterize this fibronectin binding protein from S aureus, the gene for this protein has been cloned in E. coli. The fibronectin binding domain within this protein has also been localized.